The present application relates to electronic devices, and in particular, to electronic patches that can adhere to human skin or the surface of an object.
Electronic patches or stickers can be attached to human bodies and other objects such as merchandized goods such as computers, machineries, and clothes, packaging material and shipping boxes. Electronic patches can communicate with smart phones or other devices wirelessly, through NFC, Bluetooth, WiFi, or other methods. Tags wearable by people are a specific type of electronic patches.
Electronic patches can be used for tracking objects and for performing functions such as producing sound, light or vibrations, and so on. As the applications and human needs become more sophisticated and complex, there are a rapidly increasing number of tasks that electronic patches are required to perform. Electronic patches are often required to be conformal to curved surfaces. In addition, the curvature of the human skin can vary overtime.
Electronic patches and wearable tags can communicate with smart phones and other devices using WiFi, Bluetooth, Near Field Communication (NFC), and other wireless technologies. NFC is a wireless communication standard that enables two devices to quickly establish communication within a short range around radio frequency of 13.56 MHz. NFC is more secure than other wireless technologies such as Bluetooth and Wi-Fi because NFC requires two devices in close proximity (e.g. less than 10 cm). NFC can also lower cost comparing to other wireless technologies by allowing one of the two devices to be passive (a passive NFC tag).
Bluetooth is another wireless technology standard for exchanging data over relatively longer distances (in tens of meters). It employs short wavelength UHF radio waves from 2.4 to 2.485 GHz from fixed or mobile devices. Bluetooth devices have evolved to meet the increasing demand for low-power solutions that is required for wearable electronics. Benefited from relatively longer reading distance and active communication, Bluetooth technologies allow wearable patches to continuously monitoring vital information without human interference, which is an advantage over NFC in many applications.
Wearable patch (or tag) is an electronic patch to be worn by a user. A wearable patch is required to stay on user's skin and operate for an extended period of time from hours to months. A wearable patch can contain a micro-electronic system that can be accessed using NFC, Bluetooth, WiFi, or other wireless technologies. An authentication wearable tag can be used as a “password” similar to a barcode. For example, it can recognize a user's smart phone for authentication purpose. A wearable patch can also be integrated with different sensors such as vital signs monitoring, motion track, skin temperature measurements, and ECG detection.
Despite recent development efforts, conventional wearable devices still face several drawbacks: they may not provide adequate comfort for users to wear them; they may not stay attached to user's body for the required length of time; they are usually not aesthetically appealing.
A wearable patch often includes multiple rigid semiconductor chips and sensors have significant thicknesses assembled on flexible printed circuits to provide sensor, computation, and communication functions. The printed circuits are typically made of flexible polymer substrates that are not deformable enough to adapt to commonly occurring shape change, the high percentage of deformations of the user's skin, which is one reason for users' discomfort when they wear these wearable patches.
Another drawback of conventional wearable patches is that the rigid polymer substrate is not very breathable. The build-up of sweat and moisture can cause discomfort and irritation to the skin, especially after wearing it for an extended period of time.
Moreover, conventional wearable patches are often not robust enough to sustain repeated elongations during body movements. Under stress, different layers in wearable patches can break or delaminate rendering the wearable patches inoperable.
Another challenge for wearable patches is that the wearer's skin may interfere with their proper operations. For example, when an antenna is placed in contact with the skin, the antenna's communication range is significantly reduced. In one example, the wireless communication range of an antenna in contact with the skin is less than half the range if the antenna is placed just 4 mm away from the user's skin.
In addition, while some sensors such as electroencephalogram (EEG) and body temperature sensors need to be in contact of users' skins to conduct measurements, other sensors such as ambient temperature sensor are required to measure signals away from the user's skin. The ambient temperature if often different from the human body temperature that is in the range of 36-41° C.
There is therefore a need for more flexible wearable electronic patches that stick to skin longer, are comfortable for users to wear, and can perform intended functions at and away from users' skins so it is not affected by body temperature.